A very simple synthetic method is proposed to prepare spiky gold nanoparticles possessing a strong and broad absorption band around the surface of temperature-sensitive poly(N-isopropylacrylamide), poly(NIPAM), particles. The structural properties of the composite particles were thoroughly characterized by UV-visible spectrophotometer, scanning electron microscope, and dynamic light scattering. These composite materials exhibited a reversible swelling and collapsing behavior above and below the lower critical solution temperature. As the surface-adsorbed spiky gold nanoparticles around the poly(NIPAM) possessed a strong and broad absorption band and exhibited the photon-to-heat conversion property, these nanocomposites also showed fast reversible structural diameter changes upon exposure to a broad band light. These types of composite particles may serve as an excellent template for the development of photothermally triggered carrier systems.